Hydrothermal corrosion of thin TiN PVD films (3 μm thickness) at 100 MPa water and 20-800 o C temperature range was studied. Noticeable oxidation starts above 200 o C and acceleration of oxidation processes takes place in hydrothermal conditions in comparison with airflow oxidation of corresponding PVD films and air oxidation of TiN powders. The formation of Ti n O 2 n - 1 homological series phases and regular single crystals in oxide scale were observed. FeTiO 3 ilmenite layer secures high protective properties at 600 o C and practically does not contain chromium. Therefore, usual low alloy steel with TiN coating can be used instead superalloy for wet air oxidation system with working temperature up to 600 o C.